The Strongyloidea

Members of this superfamily are widespread throughout the world.  They are primarily parasites of herbivores such as ruminants and horses although a few species are found in ratite birds and marsupials.

They have the following general features

They are large-bodied worms and are easily seen in situ at necropsy of infected hosts.

Males have a copulatory bursa

Most have large mouth openings and prominent buccal capsules which may contain teeth in some species. They use their buccal capsules in feeding, either by  grazing the mucosal surface or by attaching to a plug of mucosa, drawing it into the buccal capsule and digesting it.

Leaf crowns may be present as accessory cuticular structures around the opening of the buccal capsule.

Most females of this group pass strongyle-type eggs.

Some species have life cycles that include extensive migrations through the bodies of their hosts. They include the large strongyles of equines (e.g. Strongylus vulgaris), the gape worm of birds (Syngamus trachea) and the kidney worm of swine (Stephanurus dentatus).

Most have direct life cycles with infection by ingestion of infective third stage larvae but a few such as Stephanurus dentatus (the swine kidney worm) and Syngamus trachea (the gapeworm of fowl) may include earthworms as transport hosts.

Most are found in the large intestine but a few species occur in the respiratory and urinary tracts.

     Three families are important in domestic animals - Strongylidae, Chabertiidae and Syngamidae


Members of this family are common in equines but they are also found in elephants, ostriches, rhinoceros, tapirs, tortoises, warthogs and marsupials. Their predilection sites include primarily the cecum and colon. The preparasitic phases of the life cycles are similar with strongyle-type eggs passing in the feces of infected hosts. Development to the infective, ensheathed third stage larvae may take as little as 7-10 days in a warm, moist environment.

Equine strongylids are usually divided into the large strongyles, belonging to the subfamily Strongylinae and the small strongyles which are members of the subfamily Cyathostominae.


This family has been further subdivided into two subfamilies - the Chabertiinae and the Oesophagostominae.

The Chabertiinae are often called the bowel worms because of their location in the colon of their hosts. They have a prominent bell-shaped buccal capsule.

The Oesophagostominae are often called the nodular worms because their parasitic larvae provoke nodule formation in the intestines of their definitive hosts. Adults are found in the colon and are common in pigs, ruminants, primates and rodents.

The table below lists the species of this family commonly found in domestic and wild animals.



Species Hosts


Chabertiinae Castorstrongylus castoris North American beaver
Chabertia ovina Camels, cattle, chamois, deer, gazelles, goats, sheep
Ternidens deminutus African and Asian non-human primates
Oesophagostominae Oesophagostomum columbianum Sheep, goats, alpaca, antelope (African)
Oesophagostomum dentatum Pigs
Oesophagostomum radiatum Cattle, zebra, water buffalo
Oesophagostomum venulosum Ruminants - primarily sheep and goats
Oesophagostomum quadrispinulatum Pigs



The syngamids are found mainly in the respiratory systems of birds and mammals but one species occurs in the urinary tract of swine and another occurs in the intestines of porcupines. There are two subfamilies, the Stephanurinae and the Syngaminae. Examples of species occurring in domestic and wild animals and birds are given in the following table.


Family Subfamily Species Hosts
Syngamidae Stephanurinae Stephanurus dentatus Swine
Syngaminae. Cyathostoma bronchialis Ducks, geese, swans
Mammomonogamus spp Cattle, sheep, goats, deer, felids and elephants in the tropics
Syngamus trachea Birds primarily quail, pheasants, guinea fowl





Parasites and Parasitic Diseases of Domestic Animals
Dr. Colin Johnstone (principal author)
Copyright 1998 University of Pennsylvania
This page was last modified on January 24, 2000